Agricultural blend and process of forming an agricultural blend

ABSTRACT

The present intention relates to an agricultural blend and a method of forming an agricultural blend. The agricultural blend includes a sulfate source and calcium silicate or a by-product of slag, the slag being selected from the group consisting of steel slag, stainless steel slag, alloy steel slag, carbon steel slag, and phosphate slag. The method includes blending a sulfate source and calcium silicate.

FIELD OF THE INVENTION

The present invention is directed to agricultural blends and processes of forming agricultural blends. More specifically, the present invention is direct to including by-products from industrial processes in agricultural blends.

BACKGROUND OF THE INVENTION

Specific minerals are known to stimulate growth in agriculture. Fertilizers and other additives can include minerals such as calcium silicate, magnesium silicate, potassium silicate, and sodium silicate. Similarly, compounds such as gypsum (CaSO₄H₂O) can be used in agriculture (for example, as a soil stabilizer). Fertilizers and the other additives can deliver these minerals, these compounds, or combinations of these minerals and these compounds. The method of delivering the minerals or compounds, the crystal structure of the minerals or compounds, and the combination of the minerals or compounds impacts the efficacy of the fertilizers and other additives.

The minerals or compounds in the fertilizers or other additives can be natural (for example, mined) or synthetic (for example, a by-product of an industrial processes). Utilizing by-products can be environmentally beneficial by reducing waste and economically beneficial by creating economic value to existing waste. As described in U.S. Pat. No. 5,362,471, which is incorporated by reference in its entirety, synthetic gypsum is generally obtained as a by-product in the manufacture of phosphate containing fertilizers and as a by-product in the desulfurization of flue gas. According to U.S. Pat. No. 5,362,471, the synthetic gypsum has not experienced widespread commercial success because it has a different crystal size and shape than natural gypsum.

Another process of obtaining synthetic gypsum is described in U.S. Pat. No. 5,510,094, which is incorporated by reference in its entirety. The process described in U.S. Pat. No. 5,510,094 relates to treating the synthetic gypsum with ammonia and shows that a synthetic gypsum by-product from coal combustion can be used for agriculture upon being scrubbed with a slurry containing ammonia. The process does not include the combination of minerals that promote growth. Treating synthetic gypsum with anhydrous ammonia or a slurry containing ammonia can create an inhalation hazard with potential release of ammonia gas.

U.S. Pat. No. 6,939,387, which is incorporated by reference in its entirety, discloses a soil enhancer for use in the agriculture industry that does include certain minerals promoting growth. The patent disparages a product containing MgSiO3 as being unable to provide sufficient silicon to plants for a sustained period of time without frequent applications. The patent also disparages a product having at least 15% of a resulting pellet coming from a calcium source such as gypsum from cement operations as not permitting enough silica to be applied without applying large amounts of pellets. The patent describes a composition including a calcium silicate slag (specifically, a by-product of mining operations), magnesium sulfite particles, and water in a ratio of about 20:4:1 for a non-granulated compound and about 2:7:4 for a granulated compound. The combination suffers from the drawbacks that it does not have the soil stabilizing effects of gypsum, does not utilize by-products from processes other than mining, does not include the benefits of magnesium silicate, and calcium silicate. This combination is only able to provide enough soluble silicon under acidic soil conditions.

What is needed is an agricultural product and a method of forming an agricultural product that provides a sulfate source and calcium silicate that does not suffer from the drawbacks of the prior art.

SUMMARY OF THE INVENTION

An exemplary embodiment of the present invention includes an agricultural blend, the agricultural blend including a sulfate source and calcium silicate.

Another exemplary embodiment of the present invention includes an agricultural blend, the agricultural blend including synthetic gypsum and a by-product of slag, the slag being selected from the group consisting of steel slag, stainless steel slag, alloy steel slag, carbon steel slag, and phosphate slag.

Another exemplary embodiment of the present invention includes a method of forming an agricultural blend, the method including blending a sulfate source and calcium silicate.

One advantage of an embodiment of the present invention includes the environmental benefits associated with utilizing a waste stream or by-product from coal combustion in a useful manner.

Another advantage of an embodiment of the present invention includes environmental benefits associated with utilizing a waste stream or by-product from slag in industrial processes.

Another advantage of an embodiment of the present invention includes improved ability for calcium silicate and/or magnesium silicate to be retained in agricultural substances for longer periods of time.

Another advantage of an embodiment of the present invention includes improved ability to blend the calcium silicate/synthetic gypsum combination with various sources of nitrogen (such as monoammonium phosphate diammonium phosphate) without the risk of an ammonia flash).

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Provided is an agricultural blend and a process of forming an agricultural blend. The agricultural blend can be, can be a portion of, or can include a fertilizer, a mineral soil amendment (for example, calcium and magnesium silicate), a soil conditioner (for water and stress management, the enhancement of plant vitality, the improvement of soil water and air movement, nutrient holding capacity, or combinations thereof); a liming agent (for example, calcium and magnesium silicate), an additive to improve soil pH, an additive to decrease metal toxicity issues, or any combination thereof The agricultural blend can be environmentally-friendly by utilizing waste or by-product streams from one or more industrial processes. For example, in one embodiment, the agricultural blend can be formed from a by-product of coal combustion and a by-product of stainless steel slag.

In one embodiment, the agricultural blend includes a sulfate source and calcium silicate. The sulfate source can be any suitable non-hazardous sulfate source including, but not limited to, gypsum. The gypsum can be mined, synthetic, or a combination thereof Using mined gypsum, synthetic gypsum, and combinations of mined gypsum and synthetic gypsum permits the effects of the structure of the gypsum to be controlled and/or adjusted. The synthetic gypsum can be from any suitable industrial process resulting in a desired concentration of sulfate. For example, in one embodiment, the synthetic gypsum can be a by-product of flue gas desulfurization in a coal combustion process.

Coal includes sulfur oxides (SOx). Monitoring emissions in coal combustion involves monitoring whether SOx is being emitted. To reduce SOx, various scrubbers or other systems remove sulfur, sulfates, sulfites, sulfur tiroxide, sulfur dioxide, or other sulfur-containing compounds. The SOx can be reduced and/or removed by flue gas desulfurization which involves circulating flue gas to remove sulfur from the flue gas and generating a by-product that includes the sulfur. There are two different methods of performing flue gas desulfurization that produce synthetic gypsum as a by-product. In a first method (assuming ideal operating conditions), wet scrubbing is performed with a CaCO₃ slurry (for example, a limestone slurry) to produce CaSO₃ (calcium sulfite):

CaCO₃(solid)+SO₂(gas)→CaSO₃(solid)+CO₂(gas)  (1)

In a second method (assuming ideal operating conditions), wet scrubbing is performed with a Ca(OH)₂ slurry (for example, a lime slurry) to produce CaSO₃ (calcium sulfite):

Ca(OH)₂(solid)+SO₂(gas)→CaSO₃(solid)+H₂O(liquid)  (2)

After the CaSO₃ (calcium sulfite) is formed (either under the first method or the second method), it undergoes a forced oxidation process which converts it to CaSO₄ (for example, synthetic gypsum):

CaSO₃(solid)+H₂O(liquid)+½O₂(gas)→CaSO₄(solid)+H₂O  (3)

In operation, the lime or limestone slurry is present with the synthetic gypsum after the flue gas desulfurization. Depending upon the concentration of sulfur in the coal and the other limiting aspects of the reactions, the by-product of the flue gas desulfurization can include a predetermined amount of synthetic gypsum and lime or limestone. In one embodiment, the by-product of the flue gas desulfurization includes about 90% to about 95% calcium sulfate (CaSO₄-2H₂0), about 1% to about 2% calcium sulfite (CaSO₃-½H₂), and about 2% to about 3% calcium carbonate (CaCO₃). The remaining portion can include magnesium sulfate/sulfite.

The by-product of the flue gas desulfurization is further processed to achieve desired physical properties. For example, the by-product can be filtered through one or more mesh stages. In one embodiment, 99% of the by-product is smaller than #20 mesh, 90% of the by-product is smaller than #60 mesh, 75% of the by-product is smaller than #100 mesh. Additionally or alternatively, moisture content can be adjusted to a predetermined range (for example, by a mechanical watering devices, filters, centrifuges, or combinations thereof). The predetermined range of moisture content can be between about 10% and about 18%, between about 10% and about 15%, between about 7% and about 12%, between about 5% and about 7%, or at about 5%. In one embodiment, the lime or limestone forms about 90% to about 99% of the by-product. In another embodiment, the gypsum forms about 90% to about 99% of the by-product.

Additionally or alternatively, the sulfate source can be a by-product of other industrial processes. For example, the sulfate source can be a by-product formed from slag in a coal combustion process, a by-product formed from bottom-boiler ash in a coal combustion process, a by-product formed from hydrogen sulfide produced from a pickling liquor, or any suitable combination thereof.

In one embodiment, the sulfate source includes ammonium sulfate. In this embodiment, instead of using the lime or limestone slurry, ammonia may be used as a reactant in an industrial process (such as flue gas desulfurization in coal combustion) to yield (NH₄)₂SO₄ (ammonium sulfate). However, since the composition is chemically different from gypsum, the use and application of the resulting agricultural blend may differ from the use and application of the embodiment including gypsum. In addition, the pH of the resulting component is higher, thereby permitting a blending of the ammonium sulfate and the by-product of flue gas desulfurization (or other sulfate source) to achieve a desired pH.

The calcium silicate blended with the sulfate source can be from any suitable source. The calcium silicate can be any suitable non-hazardous industrial by-product including, but not limited to, a by-product from stainless steel slag, a by-product from alloy steel slag, or any suitable combination thereof. In one embodiment, the calcium silicate is blended with magnesium silicate, which can be formed of mined magnesium silicate, synthetic magnesium silicate, or a combination thereof.

In one embodiment, the calcium silicate by-product contains calcium, magnesium, and silicon. The calcium can form about 26% to about 28% of the by-product. The magnesium can form about 6% to about 8% of the by-product. The silicon can form about 30% to about 39% of the by-product. The by-product can include soluble silicon providing greater than about 10 lbs/ton.

The sulfate source, calcium silicate, and other suitable components are blended together by high speed blending to form the agricultural blend. The agricultural blend is a colloidal suspension. The agricultural blend can be in any suitable form for delivery to plants, soil, or other agricultural substances. For example, the blend can be pelletized or agglomerated, which may involve including additional components such as binders.

In one embodiment, the composition of the agricultural blend includes about 75% to about 95% sulfate source and about 5% to about 25% calcium silicate by weight. In one embodiment, the agricultural blend includes about 88.5% sulfate source and about 12.5% calcium silicate. The combined wet blend of the agricultural blend can include about 5% to about 6% H₂O, about 20% to about 24% calcium, about 4% to about 6% magnesium, and about 17% to about 19% sulfur. In one embodiment, the wet blend of the agricultural blend includes about 5.6% H₂O, about 22.2% calcium, about 0.05% magnesium, and about 17.5% sulfur. The combined dry blend of the agricultural blend can include about 22% to about 26% calcium, about 0.04% to about 0.06% magnesium, and about 17.5% to about 19.5% sulfur. In one embodiment, the dry blend of the agricultural blend includes about 23.5% calcium, about 0.05% magnesium, and about 18.5% sulfur. The pH of the agricultural blend can be about 7.5 to 8.5 or about 8.1. However, as discussed above, the pH can be raised by including ammonium sulfate.

The agricultural blend can improve handling by 25%, can improve flow ability by 15%, and/or can improve storability 30%.

While the invention has been described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the appended claims. 

What is claimed is:
 1. An agricultural blend, comprising: a sulfate source; and calcium silicate.
 2. The agricultural blend of claim 1, wherein the sulfate source includes a greater concentration of sulfates than sulfites.
 3. The agricultural blend of claim 1, wherein the sulfate source includes mined gypsum.
 4. The agricultural blend of claim 1, wherein the sulfate source includes synthetic gypsum.
 5. The agricultural blend of claim 1, wherein the sulfate source is a non-hazardous industrial by-product.
 6. The agricultural blend of claim 1, wherein the sulfate source is a by-product formed by flue gas desulfurization in a coal combustion process.
 7. The agricultural blend of claim 1, wherein the sulfate source is a by-product formed from slag in a coal combustion process.
 8. The agricultural blend of claim 1, wherein the sulfate source is a by-product formed from bottom boiler ash in a coal combustion process.
 9. The agricultural blend of claim 1, wherein the sulfate source is a by-product formed from hydrogen sulfide produced from a pickling liquor.
 10. The agricultural blend of claim 1, wherein the sulfate source includes ammonium sulfate.
 11. The agricultural blend of claim 1, wherein the calcium silicate is blended with magnesium silicate.
 12. The agricultural blend of claim 1, wherein the calcium silicate is a by-product from steel slag.
 13. The agricultural blend of claim 1, wherein the calcium silicate is a by-product from alloy steel slag.
 14. The agricultural blend of claim 1, wherein the calcium silicate is a non-hazardous industrial by-product.
 15. The agricultural blend of claim 1, wherein the blend is pelletized or aggolmerated.
 16. The agricultural blend of claim 1, further comprising mined magnesium silicate.
 17. The agricultural blend of claim 1, further comprising synthetic magnesium silicate.
 18. An agricultural blend, comprising: synthetic gypsum; and a by-product of slag, the slag being selected from the group consisting of steel slag, stainless steel slag, alloy steel slag, carbon steel slag, and phosphate slag.
 19. A method of forming an agricultural blend, the method comprising blending a sulfate source and calcium silicate.
 20. The method of claim 19, further comprising processing the agricultural blend to form pellets. 